Merge branch 'kb/full-history-compute-treesame-carefully-2'

Major update to the revision traversal logic to improve culling of
irrelevant parents while traversing a mergy history.

* kb/full-history-compute-treesame-carefully-2:
  revision.c: make default history consider bottom commits
  revision.c: don't show all merges for --parents
  revision.c: discount side branches when computing TREESAME
  revision.c: add BOTTOM flag for commits
  simplify-merges: drop merge from irrelevant side branch
  simplify-merges: never remove all TREESAME parents
  t6012: update test for tweaked full-history traversal
  revision.c: Make --full-history consider more merges
  Documentation: avoid "uninteresting"
  rev-list-options.txt: correct TREESAME for P
  t6111: add parents to tests
  t6111: allow checking the parents as well
  t6111: new TREESAME test set
  t6019: test file dropped in -s ours merge
  decorate.c: compact table when growing

3 files changed, 247 insertions, 7 deletions

diff --git a/t/t6012-rev-list-simplify.sh b/t/t6012-rev-list-simplify.sh
index dd6dc844e7..57ce2395d6 100755
--- a/t/t6012-rev-list-simplify.sh
+++ b/t/t6012-rev-list-simplify.sh
@@ -14,21 +14,24 @@ unnote () {
 
 test_expect_success setup '
 	echo "Hi there" >file &&
-	git add file &&
-	test_tick && git commit -m "Initial file" &&
+	echo "initial" >lost &&
+	git add file lost &&
+	test_tick && git commit -m "Initial file and lost" &&
 	note A &&
 
 	git branch other-branch &&
 
 	echo "Hello" >file &&
-	git add file &&
-	test_tick && git commit -m "Modified file" &&
+	echo "second" >lost &&
+	git add file lost &&
+	test_tick && git commit -m "Modified file and lost" &&
 	note B &&
 
 	git checkout other-branch &&
 
 	echo "Hello" >file &&
-	git add file &&
+	>lost &&
+	git add file lost &&
 	test_tick && git commit -m "Modified the file identically" &&
 	note C &&
 
@@ -37,7 +40,9 @@ test_expect_success setup '
 	test_tick && git commit -m "Add another file" &&
 	note D &&
 
-	test_tick && git merge -m "merge" master &&
+	test_tick &&
+	test_must_fail git merge -m "merge" master &&
+	>lost && git commit -a -m "merge" &&
 	note E &&
 
 	echo "Yet another" >elif &&
@@ -105,9 +110,21 @@ check_result 'L K J I H G F E D C B A' --full-history
 check_result 'K I H E C B A' --full-history -- file
 check_result 'K I H E C B A' --full-history --topo-order -- file
 check_result 'K I H E C B A' --full-history --date-order -- file
-check_outcome failure 'I E C B A' --simplify-merges -- file
+check_result 'I E C B A' --simplify-merges -- file
 check_result 'I B A' -- file
 check_result 'I B A' --topo-order -- file
 check_result 'H' --first-parent -- another-file
 
+check_result 'E C B A' --full-history E -- lost
+test_expect_success 'full history simplification without parent' '
+	printf "%s\n" E C B A >expect &&
+	git log --pretty="$FMT" --full-history E -- lost |
+	unnote >actual &&
+	sed -e "s/^.*	\([^ ]*\) .*/\1/" >check <actual &&
+	test_cmp expect check || {
+		cat actual
+		false
+	}
+'
+
 test_done
diff --git a/t/t6019-rev-list-ancestry-path.sh b/t/t6019-rev-list-ancestry-path.sh
index dd5b0e55d2..dabebaee0b 100755
--- a/t/t6019-rev-list-ancestry-path.sh
+++ b/t/t6019-rev-list-ancestry-path.sh
@@ -16,6 +16,10 @@ test_description='--ancestry-path'
 #
 #  F...I                 == F G H I
 #  --ancestry-path F...I == F H I
+#
+#  G..M -- G.t                 == [nothing - was dropped in "-s ours" merge L]
+#  --ancestry-path G..M -- G.t == L
+#  --ancestry-path --simplify-merges G^..M -- G.t == G L
 
 . ./test-lib.sh
 
@@ -89,6 +93,29 @@ test_expect_success 'rev-list --ancestry-path F...I' '
 	test_cmp expect actual
 '
 
+# G.t is dropped in an "-s ours" merge
+test_expect_success 'rev-list G..M -- G.t' '
+	>expect &&
+	git rev-list --format=%s G..M -- G.t |
+	sed -e "/^commit /d" >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'rev-list --ancestry-path G..M -- G.t' '
+	echo L >expect &&
+	git rev-list --ancestry-path --format=%s G..M -- G.t |
+	sed -e "/^commit /d" >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'rev-list --ancestry-path --simplify-merges G^..M -- G.t' '
+	for c in G L; do echo $c; done >expect &&
+	git rev-list --ancestry-path --simplify-merges --format=%s G^..M -- G.t |
+	sed -e "/^commit /d" |
+	sort >actual &&
+	test_cmp expect actual
+'
+
 #   b---bc
 #  / \ /
 # a   X
diff --git a/t/t6111-rev-list-treesame.sh b/t/t6111-rev-list-treesame.sh
new file mode 100755
index 0000000000..88b84dfa73
--- /dev/null
+++ b/t/t6111-rev-list-treesame.sh
@@ -0,0 +1,196 @@
+#!/bin/sh
+#
+#        ,---E--.   *H----------.             * marks !TREESAME parent paths
+#       /        \ /             \*
+# *A--*B---D--*F-*G---------K-*L-*M
+#   \     /*       \       /
+#    `-C-'          `-*I-*J
+#
+# A creates "file", B and F change it.
+# Odd merge G takes the old version from B.
+# I changes it, but J reverts it, so K is TREESAME to both parents.
+# H and L both change "file", and M merges those changes.
+
+test_description='TREESAME and limiting'
+
+. ./test-lib.sh
+
+note () {
+	git tag "$1"
+}
+
+unnote () {
+	git name-rev --tags --stdin | sed -e "s|$_x40 (tags/\([^)]*\))\([ 	]\)|\1\2|g"
+}
+
+test_expect_success setup '
+	test_commit "Initial file" file "Hi there" A &&
+	git branch other-branch &&
+
+	test_commit "file=Hello" file "Hello" B &&
+	git branch third-branch &&
+
+	git checkout other-branch &&
+	test_commit "Added other" other "Hello" C &&
+
+	git checkout master &&
+	test_merge D other-branch &&
+
+	git checkout third-branch &&
+	test_commit "Third file" third "Nothing" E &&
+
+	git checkout master &&
+	test_commit "file=Blah" file "Blah" F &&
+
+	test_tick && git merge --no-commit third-branch &&
+	git checkout third-branch file &&
+	git commit &&
+	note G &&
+	git branch fiddler-branch &&
+
+	git checkout -b part2-branch &&
+	test_commit "file=Part 2" file "Part 2" H &&
+
+	git checkout fiddler-branch &&
+	test_commit "Bad commit" file "Silly" I &&
+
+	test_tick && git revert I && note J &&
+
+	git checkout master &&
+	test_tick && git merge --no-ff fiddler-branch &&
+	note K
+
+	test_commit "file=Part 1" file "Part 1" L &&
+
+	test_tick && test_must_fail git merge part2-branch &&
+	test_commit M file "Parts 1+2"
+'
+
+check_outcome () {
+	outcome=$1
+	shift
+
+	case "$1" in
+	*"("*)
+		FMT="%P	%H | %s"
+		munge_actual="
+			s/^\([^	]*\)	\([^ ]*\) .*/(\1)\2/
+			s/ //g
+			s/()//
+		"
+		;;
+	*)
+		FMT="%H | %s"
+		munge_actual="s/^\([^ ]*\) .*/\1/"
+		;;
+	esac &&
+	printf "%s\n" $1 >expect &&
+	shift
+
+	param="$*" &&
+	test_expect_$outcome "log $param" '
+		git log --format="$FMT" $param |
+		unnote >actual &&
+		sed -e "$munge_actual" <actual >check &&
+		test_cmp expect check || {
+			cat actual
+			false
+		}
+	'
+}
+
+check_result () {
+	check_outcome success "$@"
+}
+
+# Odd merge G drops a change in F. Important that G is listed in all
+# except the most basic list. Achieving this means normal merge D will also be
+# shown in normal full-history, as we can't distinguish unless we do a
+# simplification pass. After simplification, D is dropped but G remains.
+# Also, merge simplification of G should not drop the parent B that the default
+# simple history follows.
+check_result 'M L K J I H G F E D C B A'
+check_result '(LH)M (K)L (GJ)K (I)J (G)I (G)H (FE)G (D)F (B)E (BC)D (A)C (A)B A'
+check_result 'M H L K J I G E F D C B A' --topo-order
+check_result 'M L H B A' -- file
+check_result '(LH)M (B)L (B)H (A)B A' --parents -- file
+check_result 'M L J I H G F D B A' --full-history -- file
+check_result '(LH)M (K)L (GJ)K (I)J (G)I (G)H (FB)G (D)F (BA)D (A)B A' --full-history --parents -- file
+check_result '(LH)M (G)H (J)L (I)J (G)I (FB)G (B)F (A)B A' --simplify-merges -- file
+check_result 'M L K G F D B A' --first-parent
+check_result 'M L G F B A' --first-parent -- file
+
+# Check that odd merge G remains shown when F is the bottom.
+check_result 'M L K J I H G E' F..M
+check_result 'M H L K J I G E' F..M --topo-order
+check_result 'M L H' F..M -- file
+check_result '(LH)M (B)L (B)H' --parents F..M -- file
+check_result 'M L J I H G' F..M --full-history -- file
+check_result '(LH)M (K)L (GJ)K (I)J (G)I (G)H (FB)G' F..M --full-history --parents -- file
+check_result '(LH)M (G)H (J)L (I)J (G)I (FB)G' F..M --simplify-merges -- file
+check_result 'M L K J I H G' F..M --ancestry-path
+check_result 'M L J I H G' F..M --ancestry-path -- file
+check_result '(LH)M (K)L (GJ)K (I)J (G)I (G)H (FE)G' F..M --ancestry-path --parents -- file
+check_result '(LH)M (G)H (J)L (I)J (G)I (FE)G' F..M --ancestry-path --simplify-merges -- file
+check_result 'M L K G' F..M --first-parent
+check_result 'M L G' F..M --first-parent -- file
+
+# Note that G is pruned when E is the bottom, even if it's the same commit list
+# If we want history since E, then we're quite happy to ignore G that took E.
+check_result 'M L K J I H G' E..M --ancestry-path
+check_result 'M L J I H' E..M --ancestry-path -- file
+check_result '(LH)M (K)L (EJ)K (I)J (E)I (E)H' E..M --ancestry-path --parents -- file
+check_result '(LH)M (E)H (J)L (I)J (E)I' E..M --ancestry-path --simplify-merges -- file
+
+# Should still be able to ignore I-J branch in simple log, despite limiting
+# to G.
+check_result 'M L K J I H' G..M
+check_result 'M H L K J I' G..M --topo-order
+check_result 'M L H' G..M -- file
+check_result '(LH)M (G)L (G)H' G..M --parents -- file
+check_result 'M L J I H' G..M --full-history -- file
+check_result 'M L K J I H' G..M --full-history --parents -- file
+check_result 'M H L J I' G..M --simplify-merges -- file
+check_result 'M L K J I H' G..M --ancestry-path
+check_result 'M L J I H' G..M --ancestry-path -- file
+check_result 'M L K J I H' G..M --ancestry-path --parents -- file
+check_result 'M H L J I' G..M --ancestry-path --simplify-merges -- file
+
+# B..F should be able to simplify the merge D from irrelevant side branch C.
+# Default log should also be free to follow B-D, and ignore C.
+# But --full-history shouldn't drop D on its own - without simplification,
+# we can't decide if the merge from INTERESTING commit C was sensible.
+check_result 'F D C' B..F
+check_result 'F' B..F -- file
+check_result '(B)F' B..F --parents -- file
+check_result 'F D' B..F --full-history -- file
+check_result '(D)F (BA)D' B..F --full-history --parents -- file
+check_result '(B)F' B..F --simplify-merges -- file
+check_result 'F D' B..F --ancestry-path
+check_result 'F' B..F --ancestry-path -- file
+check_result 'F' B..F --ancestry-path --parents -- file
+check_result 'F' B..F --ancestry-path --simplify-merges -- file
+check_result 'F D' B..F --first-parent
+check_result 'F' B..F --first-parent -- file
+
+# E...F should be equivalent to E F ^B, and be able to drop D as above.
+check_result 'F' E F ^B -- file # includes D
+check_result 'F' E...F -- file # includes D
+
+# Any sort of full history of C..F should show D, as it's the connection to C,
+# and it differs from it.
+check_result 'F D B' C..F
+check_result 'F B' C..F -- file
+check_result '(B)F (A)B' C..F --parents -- file
+check_result 'F D B' C..F --full-history -- file
+check_result '(D)F (BC)D (A)B' C..F --full-history --parents -- file
+check_result '(D)F (BC)D (A)B' C..F --simplify-merges -- file
+check_result 'F D' C..F --ancestry-path
+check_result 'F D' C..F --ancestry-path -- file
+check_result 'F D' C..F --ancestry-path --parents -- file
+check_result 'F D' C..F --ancestry-path --simplify-merges -- file
+check_result 'F D B' C..F --first-parent
+check_result 'F B' C..F --first-parent -- file
+
+
+test_done